hmm, been having some issues with my DFi mobo, for some reason when I try to do the update from Vista to, Vista again(to use the upgrade product key I have) it simply won't let me, errors out every time for no reason. Windows 7 installed fine so trying that at the moment so I can't really compare stability/overclocks easily.
3.8Ghz is pretty damn easy, almost on stock volts, though running higher volts at the moment to see if I can get further or increase stable overclock of HT or NB.
NB 11 multi runs fine at 220 or below, giving about 2.4Ghz NB, and you certainly see a drop in latency and an increase in performance. As to cpu scaling, I haven't run much yet, but 3dmark03, with a 4870x2, goes from 56k stock, to 83k at 3.55Ghz or so with the northy at around 2.4Ghz which is not at all a bad increase. likewise 05 went from 16k to 25k ish i think.
The HT multiplier doesn't seem to work on this mobo so can only increase it via increasing the HTT bus speed, this is fairly hard to do with lack of memory dividers and cheapo £40 4gb set, 225Mhz is fine but higher and I start to have problems.
So far what seems almost rock solid is 3.65Ghz with 2.35Ghz NB and 1.95Ghz HT. Theres issues with certain dividers/multi's with this bios on the NB/HT so finding a trade off is what I'm doing at the moment. Thing is in general with p1's the idea was the chip didn't run well with the HT less than half the speed of the cpu. So you're set to 3.6Ghz, after that you really want to bring the HT speed up to 2Ghz or more to go higher more easily.
Much as I've always liked DFi this board is doing my head in, might just be a slightly duff board and a replacement would be better, not sure tbh.
I'm barely kicking out any heat from the cpu at this speed/voltage though so 99% sure it has a lot more overhead in it, just not sure I'll get it with this mobo.